Mintage industry is getting more competitive in the global market due to the reduction of the native market in accordance with the change of social environment; therefore many corporators are attempting monopolistic supply through specific standard setting. The purpose of this study is to determine the optimum conditions of the surface treatment process which influences the new paper pH. In this paper, DOE (Design Of Experiments) is used to determine the optimum condition of the surface treatment process for practical field application. The output variable was selected as paper pH and the input variables were selected as four chemicals. The experiments were conducted as full factorial experiments by 2-level, 4-factors. Through the design of experiments, the results of this study verified main effects and interaction effects of the input variables, derived a regression model and optimum conditions of the surface treatment process for paper pH using the response optimizer.